The land management activities discussed in Section 4.4
are all "human-induced" in the sense that they are carried out by people, usually
in intentional efforts to produce food, fiber, and other goods and services
that people need or desire. There have been discussions, however, about whether
changes in carbon stocks to be reported for credit need to be limited to those
that were the direct result of that human activity; those questions are discussed
elsewhere in this Special Report (e.g., Section 2.3.3.1).

If it is decided to limit reportable amounts to reduced emissions or increased
sinks resulting from "direct human-induced" activities (as the term appears,
for example, in Article 3.3), separation of natural from direct and indirect
human effects can be approximated in some situations by the application of one
or more of the following techniques:

Model-based inference

Control plots where "no-treatment" regime is monitored

Specification of agreed natural-plus-indirect human-induced background corrections.
One option might be a baseline or "business-as-usual" scenario from which
to estimate the net addition attributable to the additional activities undertaken
under Article 3.4. The implications of different options for calculating baselines
are discussed in Section 4.6 and Chapter
2.

Some of the situations that might be created under potential Article 3.4 activities
will provide relatively easy opportunities to separate the direct effects of
an activity from those that might be either indirect (i.e., CO2, N, or S fertilization
from anthropogenic atmospheric changes) or the result of natural variability
in climate conditions. If the narrow definition of activity is chosen, for example,
many activities could be applied next to a control plot where the activity was
not applied. The carbon stock difference, if any, measured on the two areas
would be an indication of the effect of the activity.

In other situations-such as where land-use change is involved (i.e., conversion
of cropland to grass)-field operations will be unable to test how the grass
would have impacted soil carbon stocks in the absence of indirect effects or
natural variation. If a broad definition of activity is chosen, a wholesale
change in management (i.e., an improved grazing system over a large area) may
be equally difficult to test for indirect effects because retaining an exact
model of the prior management system for comparison will be difficult or impossible.